Polyalkylmethacrylates as pour point depressants for lubricating oils

ABSTRACT

POUR POINTS OF LUBRICATING OILS WITH WIDELY VARYING VISCOSITIES ARE DEPRESSED BY ADDING THERETO SMALL AMOUNTS OF NOVEL OIL SOLUBLE POLYALKYLMETHACRYLATES.

United States Patent 7 m. (:1. cos: 3764, 3/66, 15/18 U.S. Cl. 260-861 E Claims ABSTRACT OF THE DISCLOSURE Pour points of lubricating oils with widely varying viscosities are depressed by adding thereto small amounts of novel oil soluble polyalkylmethacrylates.

This is a division of application Ser. No. 753,777, filed Aug. 19, 1968, now U.S. Pat. No. 3,598,736.

This invention relates to novel oil soluble polyalkylmethacrylates which can be effectively used in lubricating oil compositions to reduce the pour point.

It is known in the art that certain polymeric materials exhibit the property of lowering pour point of lubricating oils. The influence on the pour point of an oil by any particular polymer, however, is unpredictable. Some polymers actually increase pour points, while others are effective in reducing pour points only if used in large concentrations or with lubricating oils of a specific viscosity range. The development of a pour point depressant which could be used in small concentrations yet be effective over a wide range of viscosities would be extremely desirable.

It has been found that a group of novel oil-soluble polyalkylmethacrylates with a special structure possess the aforementioned characteristics. The present additive consists of polyalkyl methacrylates wherein the alkyl group has from -20 carbon atoms and meet the following three requirements:

(1) The average number of carbon atoms of the alkyl chains in the methacrylates is between 13.8 and 14.8

(2) The molar percentage of the alkyl methacrylates with branched alkyl chains is between 10 and 30.

(3) The molar percentage of the alkyl methacrylates with an odd number of carbon atoms in the alkyl chain is between 20 and 50.

Preference is given to polyalkyl methacrylates in which the average number of carbon atoms in the alkyl chains is between 14.0 and 14.6 and to polyalkyl methacrylates in which the molar percentage of the alkyl methacrylates with branched alkyl chains is between and 25.

The novel polyalkyl methacrylates are obtained by polymerization of a mixture of alkyl methacrylates at least part of which consists of alkyl methacrylates with 10-20 carbon atoms in the alkyl group. By the correct choice of the nature of the alkyl chains in the alkyl methacrylates with 10-20 carbon atoms in the alkyl group, and of the mutual ratio by weight of these alkyl methacrylates in the mixture to be polymerized a simple process yields polymers meeting the three afore-mentioned criteria. These polymers are capable not only of considerably depressing the pour point of light lubricating oils, such as spindle oil and light machine oil, but show in addition a high activity as pour point depressants in heavy lubricating oils rich in residual components, such as heavy machine oil.

In addition to the alkyl methacrylates with 10-20 carbon atoms in the alkyl group, the monomer mixture may also contain other alkyl methacrylates. These can comprise both alkyl methacrylates with less than 10 carbon atoms in the alkyl group or alkyl methacrylates'with more than 20 carbon atoms in the alkyl group. The copolymerization of alkyl methacrylates with less than 10 carbon atoms in the alkyl group in the preparation of the poly mers is desirable if the addition of these polymers to a lubricating oil is intended to improve the viscosity index (VI) as well as the pour point of the oil. Polymers prepared from alkyl methacrylates with less than 10 carbon atoms in the alkyl group, such as methyl methacrylates, are capable, when used in higher concentrations, of improving the VI of lubricating oils, while still displaying strong activity as pour point depressants. When these polymers are used in lower concentrations, however, their activity ,as pour point depressants is generally reduced.

If the polymers in question are to be used exclusively as pour point depressants, one should select polymers prepared by the copolymerization of a mixture of alkyl methacrylates with more than 9 carbon atoms in the alkyl group because these polymers show a high activity even at very low concentrations. Suitable polymers for the present purpose can be prepared by the polymerization of a mixture of alkyl methacrylates, part of which are derived from unbranched natural and/or synthetic alcohols with 16 and/or 18 carbon atoms, and the remaining part from a mixture of branched and unbranched synthetic alcohols with 12-15 carbon atoms. The 12-15 carbon atom alcohols can be obtained by reacting a mixture of olefins with 11-14 carbon atoms with carbon monoxide and hydrogen in the presence of a complex catalyst consisting of cobalt, carbon monoxide and a phosphorus compound.

Very favorable results have been achieved using copolymers prepared in this manner. The following copolymers have exhibited exceptionally good pour point depressing activity:

(I) A copolymer of nand iso-(C -C methacrylate with n-C methacrylate, in particular a copolymer containing 76% m. of nand iso-(C C methacrylate and 24% m. of n-C methacrylate. Also a copolymer containing 85% m. of nand iso-(C -C methacrylate and 15% m. of n-C methacrylate.

(2) A copolymer of nand iso-(C -C methacrylate with n-C methacrylate, in particular a copolymer containing 74% m. of nand iso-(C -C methacrylate and 26% m. of n-C methacrylate.

(3) A copolymer of nand iso-(C -C methacrylate A with n-C methacrylate and n-C methacrylate, in particular a copolymer containing 66% m. of nand iso- (C -C methacrylate, 17% m. of n-C methacrylate and 17% m. of n-C methacrylate. Also a copolymer containing 75% m. of nand iso-(C -C methacrylate,

12% m. of n-C methacrylate and 13% m. of n-C methacrylate, and finally a copolymer containing 85 m. of nand iso-(C C methacrylate, 7% m. of n-C methacrylate and 8% m. of n-C methacrylate.

The molecular weight of the polymers according to the invention can vary within wide Polymers used as lubricating oil additives should have an average molecular weight (number average fi of between 2X 10 and 10 in particular between 5X10 and 10 The molecular weight was determined by an ebullioscopic method.

When the polymers are used as lubricating oil additives, they can be added directly to the oil or in the form of a concentrate obtained by mixing the polymers with a small quantity of oil.

The concentration in which the polymers can be used may also vary within wide limits, dependent on the structure and the molecular weight of the polymer to be used, the nature and the quantity of the paraflin waxes present in the luboil and the pour point depressing effect to be achieved. In some cases a quantity of 0.01 w. calcureach the desired pour point. In most cases a quantity of 2.0% w. is ample. One preferably incorporates 0.05 to 0.5% -w. ;of the polymers in the lubricating oil. If the with 16 and/or -18 carbon atoms and forthe remaining part from a mixture of branched and'unbranched synthetic alcohols with 12-15 carbon atoms. This alcohol mixture has been obtained by reaction of a mixture of application 'of the polymers in question is directed to VI 5 qlefins with 11 -l 4 carbon atoms with carbon monoxide improvement as well as pour point depression, it may be and hydrogen in the presenceofa complex catalyst condesirable to incorporated quantities of the polymers great- S is of a CaYbOHmOHOXide a d a 'Ph SPhOIIIS com:- er than the-aforementioned 2.0% w. pound. f Y When the polymers concerned are used as lubricating In pr p e P y according-mike n en oil additives, they can be combined with other additives the/following condltwns E- dhered t0: r 9 'f f' f additives f a defergemvficfion Monomer concentration: w for the preparation of viscosity-mcreasmg compounds, anti-corrosives, anti-foampolymers i fi '=25',000 and"42.5%' w. forthe'prepa- 111g agents-agentstoimprove the lubricating effect and f LT othercompounds which are usually added to lubricating Ia Ion 0 p0 ymers'wl 1 H oils a 15 Solvent: toluene 1 Initiator; berizoyl peroxide H 5: i l i i i Illustrated m h followmg examples Initiator concentration: 0.25% w. for the preparation of J Base 0115 v polymers with fi =25,000 and 0.30% w. for the prep- Oil Az Spindle oil with a VIoi 100 and a viscosity of aration of polymer with M :50,0 00. -f A. Redwood at 140 F. a 20 Temperature: 8090; t Oil B:'*Medium machine oil with a VI of 95 :and a Polymerization timez'24 hours. viscosity 01 160 A. Redwood at 140 F. This-oil contained The composition of'thepolymers isshown in fla-bjlel. 3.

TABLE 1; For the alkyl methacrylates with 10-20 carbon atoms in the p alkyl group we havep Molar pereentageoi alkyl Molar ratio methacrylates withr n and Average Average iso-(Cw-Cu) number 01 An odd molecular. methaerylate/ carbon nunber of weight n-Cu methatoms in 1 carbon atoms I (number. Polymer aerylate/n-Cm the alkyl branched in the average Mn)1 number methacrylate chair s k allryl chain alkyl chain thepolymers' 14.5 .20..1 37.2 25,000. 14.1 22.5 41.6 25,000 14.7 17.5 32.3 1 25,000 /1 14.3 19.9 36.9; /12/13" 143 19.0 cs9 50,000' /7/ 8-. 14.0 22.4 41.4 125,000 74/26/ .0 14.1 .19.? ass 25,000.

-- Oil C: Heavy machine oil with a VI of and a vis-' 165014.11 1 t140 F.Thi d'w e? coslty 0 W00 a S 11 50 sants were included in the investigation. 'Ilnytwere,- also w. deasphalted, refined and dewaxed short residue.

. The three base oils hade a-pour point of +15 F. (determined according to ASTM D-97) and had beenfpre-' pared from a Middle East crude. V

' Percent by weight of the various alkyl Commercial pour, point depressants For comparison, four commercial pour. point deprespolyalkyl methacrylates, but failed tomeet one or moi'e' of the criteria for the polymers according to the invention.

The composition of these commercial point depre ssants is shownin TableII;

TABLE II Molar percentage-of 1 alk yi nethaorylates withf methaerylates present in the polymers .An'oddnmnber of carbon branched; berol carbon Polymer 0x0- atoms in the alkyl atoms in the number 01 n-C1 C8-C1: n-Cu n-Cu n-Cn n-Cn alkyl chains chain alkyl chain;

Polymers according to the invention Seven polymers were prepared according to the invenacrylates'partly derived from unbranched natural alcohols To study their activity as pour point depressants, poly-' fion by copolymefization of a mixture of alkyl math 75 mers I VII and 1-4 were added in d1tferentconcentrat1ons to lube oils A, B and C. Thepour point of each lube oil composition was determined according to ASTM D-97. The results are listed in Table I11.

and (3) a number average molecular weight of 2,000 to 2,000,000, wherein the alkyl groups in said alkyl meth TABLE HI Type of oil Oil A, p.p. 15 F. Oil B, p.p. 15 F. Oil 0, p.p. 15 F.

Polymer concentration, percent w. 1 0. 2 0. 5 0. 1 O. 2 0. 5 0. 1 0. 2 0. 5

Polymer added:

Polymer I 25 Polymer IL. 25

Polymer III. 20

Polymer IV 20 30 35 15 15 20 +5 0 Polymer V.-- 20 30 -30 20 20 -20 0 Polymer VI 20 Polymer VIL -30 Polymer 1 20 15 15 15 +5 0 0 Polymer 2.-- 15 20 e Polymer 3 15 20 +5 5 15 +15 +15 +15 Polymer 4 5 10 20 The results in Table III indicate the following:

(1) In oil A the polymers according to the invention are for the most part better pour point depressants than the commercial products. Of the latter, additive 3 is the most effective.

(2) In oil B the products IV and V according to the invention are better pour point depressants than commercial additives 1 and 3.

(3) In oil C the products IV and V are at least as active as the best commercial additive. Additive 3, which in oil A gave the best performance among the commercial additives, is completely inactive in oil C.

Unlike the commercial additives tested, the polymers according to the invention olfer the significant advantage of displaying a high activity in lube oils with widely varying viscosity.

We claim as our invention:

1. Oil-soluble copolymer of polyalkyl methacrylates having (1) a molar percentage of alkyl methacrylates with branched alkyl chains between 10 and 30%, (2) a molar percentage of alkyl methacrylates having an odd number of carbon atoms in the alkyl chains between 20 and 50%,

References Cited UNITED STATES PATENTS 3,310,513 3/1967 Barie et al. 260-895 A 3,226,326 12/ 1965 Lorensen et al 260-861 E 3,238,133 3/1966 Lorensen 260-861 E HARRY WONG, JR., Primary Examiner US. Cl. X.R. 

